Signal lamp



Jan. 18, .1944. c. ADLER. JR

S IGNAL LAMP Filed Nov; 9, 1943 Patented Jan. 18, 1944 UNITED STATESPATENT OFFICE 2 Claims.

to signal lamps safety is to provide a forward signal lamp having areflector possessing critical characteristics in association with alight source disposed oil the focal point of the reflector to the endthat regardless of th position from which the lamp is viewed an area ofthe cover glass oi the lamp is visibly and arrestively illuminated. Thatis to say, beams are reflected from substantially every point of thereflector and visibly projected throughout substantially the entire areaof the cover glass as non-parallel beams. 'Ihese beams have a desirablewide angle spread, e. g., of at least 110 and assure that the pilot of adirectly approaching aircraft as well as the pilot of an indirectlyapproaching aircraft will be presented with the signal.

An additional object of the invention is to provide a lamp wherein thelight source is directly visible throughout substantially the entirearea of the cover glass. That is to say, the light source extends beyondthe confines of the reflector, and hence direct beams are visible aswell as the reflected beams.

Another object of the invention is to provide a lamp which does not addsubstantial weight or drag and can be installed without requiring thatthe current supply facilities of the aircraft be augmented.

A further object of the invention is to provide a lamp embodying the"sealed beam structure. namely a sealed chamber defined by the reflectorand cover glass which may be evacuated or evacuated and fllied with asuitable gas in accordance with the well known "sealed beam" principle,the light source such as a filament being disposed in the chamber, andpreferably fixed in relation to the reflector to produce the improvedresults. I have found that in such a. construction beams of light arereflected from substantially every point of the reflector provided thecritical reflectorstructure and disposition of the filament with respectthereto are adhered to in accordance with this invention. The presenceof a light bulb obscures some of the reflected rays. particularly"night, must (1) project centrally of the reflector and therefore thelamp does not present a signal when viewed at some angles, andfurthermore, by employing the sealed beam structure, blackening does nottake place. so that the lamp retains its emciency throughout its life.

In achieving the foregoing objects, I have found that certain criticalfeatures must be embodied in a successful lamp. By actual experiments,it has been established that the concavity of the reflector bear adirect critical relation in association with alight source located outof the focal point to the end that non-parallel beams having a wideangle spread areproduced with complete freedom from dead spots on thereflecting surface. In other words, the present lamp overcomes theobjection of having beams reflected only from the sides and top andbottom of the reflector outwardly and no beams being reflected forwardfrom the central portion of the reflector. The light source iscritically located with respect to the reflector in a manner to producereflected beams having a wide angle spread which are reflected from theentire reflecting surface of the reflector, whereby an arrestive signal1 be presented to pilots of directly and indirectl appreaching aircraft.

The present lamp has been developed after careful study of the problemsassociated with alleviating the hazards of aircraft flying at night athigh speeds, for instance 300 miles per hour or more and is to bedistinguished from aircraft landing lights or recognition lights (thelatter consuming too much current to be operated continuously),automobile headlights, railroad signals, traiiic signals, and maritimeor ships running lights. That is to say. the problem described aboverequires that a light of suitable intensity be produced which, for threedimensional flying at high speeds of 300 miles per hour or higher atintense beams of light forwardly, above and below the aircraft as wellas to the sides of the same, and (2) have a visible range greater thanthat of the usual position lights or illuminating lights.

The reflector possesses the critical characteristics of beingappreciably shallower than reflec tors heretofore employed in "sealedbeam" lamps. I find that lamps having a diameter of 3 inches or more,for instance up to 8 inches in diameter. require a. reflector having aconcavity such that a chordal line passing across the axis of thereflector comprehends the segment of a circle having an arc length ofmore than about 5 degrees and not more than about 45 degrees. In otherwords. the reflector of the present invention has substantially thecontour or curvature of the usual watch glass. The focal point of such areflector is outside of the cover glass and the light source is locatedwithin the sealed chamber closer to the reflector than to the focalpoint. The light source or filament is definitely positioned out of thefocal point of the reflector and related thereto in such a manner as toproduce with the reflector non-parallel beams of any desirable maximumangle of spread. That is to say. beams of light are reflected from allpoints or the reflector surface uniformly with some of the beams havinga widespread. e. g.. at least 110'. and the beams being of substantiallyeoual intensity. Such beams are projected through all points in thecover glass comprehended within the area defined by the beams having thewidestspread, whereby said rojected beams are visibly presentedforwardly. to the sides and above and below the lamp. and the aircrafton which the lamp is carried.

When a sealed beam lam having a reflector of the foregoincharacteristics and a li ht source positioned with respect thereto so asto produce non-parallel beams of suitably controll d s read. some ofwhich have a li ht spread of at least 110 degrees. beams are reflect dfrom everv point of the reflecting surface. as I established cnclusively by project n a beam pattern from the lamp upon a screen. Thebeam pattern was uniform throu hout its area on the screen. whereas whena lamp bulb was emnloved. or a reflector not possessin the criticalstructure. the beam patterns on the screen showed central dark areas ordead spots. It is this latter condition which the present inven ioneffectively overcomes.

In the accompanyin drawing I have illustrated one fo m of the inventionand it is to be ap reciated that chan es in dimensi n of the lamp may heresorted to w th ut de artin from the principles and discoveries hereinset forth.

In the drawing:

Fi ure 1 is a plan view partly broken awav showing the lamp positionedon an aircraft. and it is to be understood that the lam may benositioned above or below the fusela e. and on the nose as well as onthe wings. 'In fact it may be posit oned at an suitable point arallel tothe lon itudinal axis of the aircraft. and

Figure 2 is a view in section of my improved lamp.

Referring to Fi ure 2. the lam includes a concave generally circularreflector III. which is preferably s herical. The reflector is rovidedwith a marginal flange II. The cover glass i2 is generally circular andbowl shaped as shown and of a size substantiallv completely to cover thearea of the reflector. The cover glass it is provided with a marginalflange II. and the flanges H and I! are secured together at ll so as toform a sealed chamber I! defined by the cover glass and reflector afterthe manner of the usual "sealed beam lamp.

A filament of suitable candle power. e. g.. 50, y

32 or 16 is indicated at ii, and positioned within the chamber ii, onthe axis of the lamp being energized by connections I] with the currentsupply of the aircraft.

The cover glass I 2 gives a clear, 1. e., white light, or may besuitably colored to give a colored light, such as a yellow which onlyeliminatee the blue and violet rays.

When th iv-1o is insta l d on aircraft it is preferably associated witha continuous flashing mechanism not shown.

Referring again to Figure 2, for purposes of illustration I have shownthe reflector III of a dimension such that a chordal line extendingacross the center or axis from the flange II is about 4 inches. Thereflector is a segment of a circle having a wide radius, naniely alength equal to the line C-R, the letter 0 being the optical center orcenter of curvature of the reflector. The length of the arc of thesegment is about 25 degrees. The term arc as mentioned herein means thearc of the segment as described by a circle of which the point C is thecenter and coinciding with the section through the reflector shown inFigure 2. The filament It as shown is located closer to the reflectorthan to the focal point F, the latter being well outside of the coverglass;

The location of the filament in respect to the reflector, having thecharacteristics described, is also critical in that (1) an uprightenlarged virtual image is produced on the reflector but of smaller areathan the total area of the reflector, (2) non-parallel beams aredesired. (3) beams having a wide angle spread are desired and, (4) it isimportant that light be reflected from every pointof the reflectingsurface so that an arrestive illumination will be given regardless ofthe position at which the lamp is presented. In other words, the beamsare reflected from the entire area of the reflector and are projecteduniformly throughout every point of the cover glass. For example, thelight spread shown in Figure 2 encompasses at least degrees as definedby the beams W and W, and within this area, beams U are uniformlyprojected throughout the area of the cover glass.

While I have only illustrated a single central beam U and other beams Ubetween the same and the extreme beam spread W, it is to be understoodthat the number of such beams is multltudinous about the central beam Ubetween the extreme wide angle beams W, W. Hence the entire reflectingsurface of the reflector is utilized and a beam pattern on a screen fromthe lamp shown in Figure 2 will be devoid of any dark spots.

While I have described a 4-inch lamp it is to be understood that thesame critical conditions prevail in the case of a smaller lamp as wellas a larger one.

Referring further to Figure 2, beams from the filament it are directlyvisible throughout the area of the cover glass and this is particularlydesirable to provide'a signal to aircraft approaching directly from theside, at which time the direct beams D will give an adequate indication.

,1" claim:

1. A "sealed beam" running lamp for aircraft having a generally circularconcave reflector, the reflector surface being substantially free fromdead spots throughout its area, a generally circular concave coverglass, said reflector and cover glass being united at their circularedges and forming a sealed chamber in which the cover glass coverssubstantially the entire area of the reflector, and a light sourcepositioned in the sealed chamber. the said light source being locatedout of the focal point of the reflector and closer to the reflector thanto the focal point thereof. the position of the light source withrereflected from substantially the entire area of the reflectorincluding the central portion thereof, some of said reflected beamshaving a wide angle spread with respect to the lamp axis, whereby saidreflected beams are projected and are viaibic forwardly. to the sidesand above and below the lamp and the illumination is devoid of a centraldark area.

2. A "sealed beam" running lamp for aircraft according to claim 1 inwhich the light source is directly visible throughout substantially theentire area of the cover glass.

CHARLES ADLER, J a.

